How To Get Reflections On A Smooth Surface?
You are in a preview mode known as &quot;material preview&quot;. This mode uses a hidden HDRI image to provide reflections and lighting. If you look at the top right of the 3D viewport, you will see there are 4 little circles - these are the preview modes (from left to right - wireframe, solid, material, rendered). You have the second from the right selected (material preview).
Pick the one on the very right (rendered preview) to see your object with your own lighting setup. You can also press Z in the viewport and select rendered from the pie menu that appears.

If you want to see the image, click on the arrow on the right and increase the World Opacity from the menu.
If you want to set up your own image so the reflection shows but the image doesn't, in your World Shader, combine your image (Environment Texture) with a Background node with the color of your choice by mixing them with a Mix Shader, using the Is Camera Ray output of a Light Path node as the Mix Factor: